A known way to reduce friction forces and thus to lower fuel consumption consists of twisting crank drives, namely, offsetting the cylinders with respect to the center of the crankshaft. In this process, the cylinder axis is offset by a few millimeters relative to the crankshaft.
The German technical journal Motortechnische Zeitschrift (MTZ) 51 (1990) 10, p. 410ff., describes a Volkswagen VR6 engine having a twisted design, which translates into a shortened housing.
A symmetrically twisted crank drive for the above-mentioned VR6 engines is also known from MTZ 52 (1991) 3, p. 100ff.
Such a compact engine is also disclosed in German patent specification DE 197 16 274 B4.
Moreover, MTZ 62 (2001) 4, p. 280ff. describes the construction of compact V or W engines having a twisted design.
The drawback here is that it is difficult to mill such crankcases since this leads to slanted pistons and heads. In this configuration, the cylinders are positioned so as to be slanted relative to the cover surface of the cylinder crankcase. The disadvantages of this configuration lie in the mass balance or in the balancing of moments, which are not comparable to those of an inline engine, in the more laborious processing entailed by the slanted pistons, and in the associated special parts, for example, the piston and the head.
When it comes to producibility, mention should be made of the design of the water jacket, for example, the formation of the core between the cylinders, as well as of the wall thickness of the cylinder liners for rising combustion pressures. Consequently, a large cylinder distance should be seen here as being positive.
On the other hand, the total length of the engine, in other words, the compactness of the aggregate, is a very important aspect so that here, the smallest possible cylinder distance is positive.